Solid fuel heating, and in particular, cordwood fuel heating is a long-standing approach to satisfying heating requirements. Solid fuel heating technology has improved considerably through history, particularly in the area of heating efficiency and pollution control. Burning wood, especially incomplete combustion of wood, typically results in various types of air pollution including fine particulate matter and condensable organic compounds, such as creosote. Various state and federal regulatory agencies, such as the U.S. Environment Protection Agency, have promulgated various regulations directed at restricting the allowable particulate emissions for wood-burning heating appliances in an effort to reduce the environmental and health impacts of such wood-burning heating appliances. In an increasing effort to control the environmental and health impacts associated with wood-burning heating appliances, the various enacted and/or proposed regulations are not only directed at stricter emission requirements, but also at expanding the range and types of heating appliances covered by the regulations.
Many current and prior regulations have been directed at space heaters or room heaters. New and proposed regulations seek to expand the scope of regulated appliances to include whole-house heaters, also referred to as wood-burning central heating systems. Because whole-house heaters tend to use much larger fuel loads and are typically required to operate over a much broader range of outputs, many emission control technologies that have been implemented for room heaters are not readily applicable to whole house systems. In addition to the larger fuel load capacity, whole house heaters often rely on automatic control features, such as thermostatic controls, to maintain a desired set temperature in the house. The set temperature is desirably maintained across a wide range of outside temperatures. Therefore, a whole house heater must be capable of providing a wide range of heating outputs independent from the size of the fuel load, all while maintaining a high degree of combustion efficiency.